This invention pertains to a base paper comprising aramid pulp and polyvinylpyrrolidone. The paper, when coated with resin, is useful as a friction material.
U.S. Pat. No. 5,532,059 to Lee discloses a fibrous pulp of a combination of poly(p-phenylene terephthalamide) and poly(vinyl pyrrolidone) along with a process for making it. The process involves conducting a poly(p-phenylene terephthalamide polymerization reaction in the presence of poly(vinyl pyrrolidone) and the product is an improved pulp with increased fibrils and no fiber stalks.
U.S. Pat. No. 3,036,950 to Martin describes a process for depositing a water-dispersible resin on beaten cellulose pulp fibers comprising first dispersing polyvinylpyrrolidone into an aqueous slurry of said fibers, and subsequently dispersing said resin into said slurry, the polyvinylpyrrolidone being added in an amount of at least about 0.05% by weight based on the dry weight of said pulp fibers.
U.S. Pat. No. 6,139,688 to Ramachandran teaches a coated aramid fiber wherein the coating is a small amount of chitosan and the coated fiber is useful in manufacture of an improved friction paper.
There is an ongoing need to provide a paper for friction applications wherein the tensile strength of the paper can be increased with no or minimal increase in paper porosity.